Impregnation bit with improved cutting structure and blade geometry

ABSTRACT

A rotary drag bit for drilling subterranean formations and a method of forming a rotary drag bit for drilling subterranean formations comprising a bit body having a face extending from a centerline to a gage; a plurality of blades on the face generally extending radially outwardly toward the gage; and a plurality of discrete impregnated cutting posts; wherein each discrete impregnated cutting post extends outwardly from an associated one of the plurality of blades; and wherein each discrete impregnated cutting post angles generally towards a front edge of the associated blade of the discrete impregnated cutting post and generally towards the direction of rotation of the rotary drag bits. The rotary drag bit may further comprise a plurality of matrix pockets disposed on the plurality of blades, wherein the discrete impregnated cutting posts may be housed within one of the plurality of matrix pockets.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and benefit of U.S. ProvisionalApplication Ser. No. 61/156,732, filed on Mar. 2, 2009, the entiredisclosure of which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The inventions disclosed and taught herein relate generally to fixedcutter or drag type bits for drilling subterranean formations; and morespecifically related to drag bits or impregnation bits for drilling hardand/or abrasive rock formations, and especially for drilling suchformations interbedded with soft and non-abrasive layers.

2. Description of the Related Art

In order to provide background information so that the invention may becompletely understood and appreciated in its proper context, referencemay be made to a number of prior U.S. patents as follows:

U.S. Pat. No. 6,510,906 to Richert, et. al., issued Jan. 28, 2003,discloses an “impregnated bit with PDC cutters in cone area.” In oneembodiment, a drill bit employing a plurality of discrete, post-likediamond grit impregnated cutting structures extending upwardly fromabrasive particulate-impregnated blades defining a plurality of fluidpassages therebetween on the bit face is disclosed. In anotherembodiment, PDC cutters with faces oriented in the general direction ofbit rotation are placed in the cone in a bit, which is relativelyshallow, to promote enhanced drilling efficiency through softer,non-abrasive formations.

U.S. Pat. No. 6,843,333 to Richert, et. al., issued Jan. 18, 2005,discloses an “impregnated rotary bit.” In one embodiment, a drill butemploying a plurality of discrete, post-like abrasive,particulate-impregnated cutting structures extending upwardly fromabrasive, particulate-impregnating blades defining a plurality of fluidpassages therebetween on the bit fact is disclosed. In anotherembodiment, additional cutting edges may be placed in the cone of thebit surrounding the centerline thereof.

U.S. Pat. No. 6,009,962 to Beaton, issued Jan. 4, 2000 discloses an“impregnated type rotary drill bits.” In one embodiment, a rotary drillcomprises a bit body having a leading surface formed at least in partfrom solid infiltrated matrix material, a major part of the leadingsurface being impregnated with abrasive particles of a diamond or othersuperhard material. There are also mounted at plurality of largercutting element having cutting edges formed of superhard material whichproject above the surface, the larger cutting elements being so spacedas to define a substantially continuous cutting profile, so that thecutting elements in combination sweep over the whole a bottom of a holebeing drilled by the bit, during each revolution.

The inventions disclosed and taught herein are directed to andimpregnation bit with improved cutting structure and blade geometry.

BRIEF SUMMARY OF THE INVENTION

We have created a rotary drag bit for drilling subterranean formationsand a method of forming a rotary drag bit for drilling subterraneanformations comprising a bit body having a face extending from acenterline to a gage; a plurality of blades on the face generallyextending radially outwardly toward the gage; and a plurality ofdiscrete impregnated cutting posts; wherein each discrete impregnatedcutting post extends outwardly from an associated one of the pluralityof blades; and wherein each discrete impregnated cutting post anglesgenerally towards a front edge of the associated blade of the discreteimpregnated cutting post and generally towards the direction of rotationof the rotary drag bits. The rotary drag bit may further comprise aplurality of matrix pockets disposed on the plurality of blades, whereinthe discrete impregnated cutting posts may be housed within one of theplurality of matrix pockets. Each matrix pocket may support theassociated discrete impregnated cutting post of the matrix pocket,wherein the matrix pocket may facilitate cooling and cleaning.

The rotary drag bit may further comprise one or more of polycrystallinediamond compact (PDC) cutters. The plurality of discrete impregnatedcutting posts may comprise a particulate abrasive material. The bit bodymay comprise a matrix-type bit body. The plurality of discreteimpregnated cutting posts may be formed of a material comprising athermally stable diamond product (TSP).

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates an inverted perspective view of an exemplaryembodiment a of a rotary drill bit utilizing certain aspects of thepresent inventions.

FIG. 2 illustrates a schematic top elevation of portions of a pluralityof blades of the rotary drill bit of FIG. 1 comprising a plurality ofdiscrete impregnated cutting posts.

FIG. 3 illustrates a side sectional elevation of one of the plurality ofblades of the rotary drill bit of FIG. 1 comprising one of the pluralityof discrete impregnated cutting posts.

FIG. 4 illustrates a side sectional elevation of one of the plurality ofblades of the rotary drill bit of FIG. 1 comprising a plurality ofdiscrete impregnated cutting posts.

FIG. 5 illustrates a side sectional elevation of one of the plurality ofblades of the rotary drill bit of comprising a plurality of discreteimpregnated cutting posts which generally protrude perpendicular to theblade.

DETAILED DESCRIPTION

The Figures described above and the written description of specificstructures and functions below are not presented to limit the scope ofwhat Applicants have invented or the scope of the appended claims.Rather, the Figures and written description are provided to teach anyperson skilled in the art to make and use the inventions for whichpatent protection is sought. Those skilled in the art will appreciatethat not all features of a commercial embodiment of the inventions aredescribed or shown for the sake of clarity and understanding. Persons ofskill in this art will also appreciate that the development of an actualcommercial embodiment incorporating aspects of the present inventionswill require numerous implementation-specific decisions to achieve thedeveloper's ultimate goal for the commercial embodiment. Suchimplementation-specific decisions may include, and likely are notlimited to, compliance with system-related, business-related,government-related and other constraints, which may vary by specificimplementation, location and from time to time. While a developer'sefforts might be complex and time-consuming in an absolute sense, suchefforts would be, nevertheless, a routine undertaking for those of skillin this art having benefit of this disclosure. It must be understoodthat the inventions disclosed and taught herein are susceptible tonumerous and various modifications and alternative forms. Lastly, theuse of a singular term, such as, but not limited to, “a,” is notintended as limiting of the number of items. Also, the use of relationalterms, such as, but not limited to, “top,” “bottom,” “left,” “right,”“upper,” “lower,” “down,” “up,” “side,” and the like are used in thewritten description for clarity in specific reference to the Figures andare not intended to limit the scope of the invention or the appendedclaims.

We have created a rotary drag bit for drilling subterranean formationsand a method of forming a rotary drag bit for drilling subterraneanformations comprising a bit body having a face extending from acenterline to a gage; a plurality of blades on the face generallyextending radially outwardly toward the gage; and a plurality ofdiscrete impregnated cutting posts; wherein each discrete impregnatedcutting post extends outwardly from an associated one of the pluralityof blades; and wherein each discrete impregnated cutting post anglesgenerally towards a front edge of the associated blade of the discreteimpregnated cutting post and generally towards the direction of rotationof the rotary drag bits. The rotary drag bit may further comprise aplurality of matrix pockets disposed on the plurality of blades, whereinthe discrete impregnated cutting posts may be housed within one of theplurality of matrix pockets. Each matrix pocket may support theassociated discrete impregnated cutting post of the matrix pocket,wherein the matrix pocket may facilitate cooling and cleaning.

Impregnated or rotary drags bits are used conventionally for drillinghard and/or abrasive rock formations, such as sandstones. Theimpregnated drill bits typically employ a cutting face composed ofsuperhard cutting elements, such as natural or synthetic diamond grit,dispersed within a matrix of wear resistant material. As such a bitdrills, the matrix and diamonds may wear, worn cutting elements may belost and new cutting elements may be exposed. These diamond elements mayeither be natural or synthetic, and may be cast integral with the bodyof the bit, as in low-pressure infiltration, or may be preformedseparately, as in hot isostatic pressure infiltration, and attached tothe bit by brazing or furnaced to the bit by manufacturing.

Conventional impregnated bits may generally exhibit poor hydraulicdesign by employing a crow's foot to distribute fluid across the bitface and providing only a minimal flow area. Conventional impregnateddrill bits may generally exhibit poor cooling from minimal flow area.Further, conventional impregnated bits may not drill effectively whenthe bit encounters softer and less abrasive layers of rock, such asshales. When drilling through shale, or other soft formations, with aconventional impregnated drag bit the cutting structure may clog quicklyor “ball up” with the formation material making the drill bitineffective. The softer formations can also plug up fluid courses formedin the drill bit which may cause heat build up and premature wear of thebit. Therefore, when shale type formations are encountered, a morehydraulically efficient bit may be desired to achieve a higher rate ofpenetration (ROP). It follows, therefore, that selection of a bit foruse in a particular drilling operation becomes more complicated when itis expected that formations of more than one type will be encounteredduring the operation.

Thus it would be beneficial to design a drill bit which (i) wouldperform more efficiently in soft, less abrasive formations while alsoproviding adequate ROP in harder more abrasive formations withoutrequiring increased WOB during the drilling process; (ii) would providea better flow area to increase cooling; (iii) would provide additionalcutting elements; (iv) minimize the wear rate and thus increase the lifeof the drill bit and (v) the control the wear rate by modifying thecontact area through angle of attack.

FIG. 1 is an illustration of an inverted perspective view of anexemplary embodiment of a rotary drill bit utilizing certain aspects ofthe present inventions. Rotary drill bit 100 is inverted from its normalfacedown operating orientation for clarity. Rotary drill bit 100 mayinclude matrix-type body 112 having a shank 114 for connection to adrilling string (not shown) extending therefrom opposite bit face 116. Aplurality of (in this instance, ten) blades 118 extend generallyradially outwardly fashion to gage pads 120 defining junk slots 122between. The blades 118 generally extend at a right angle from a surfaceof the body 112. The plurality of blades 118 may include discreteimpregnated cutting posts (also termed discrete impregnated cuttingposts) 124, wear control elements 165 and polycrystalline diamondcompact (PDC) cutters disposed thereon extending upwardly from theblades 118. Collectively, the discrete impregnated cutting posts 124,wear control elements 165 and PDC may be termed discrete cuttingstructures.

Unlike conventional discrete impregnated cutting posts, the discreteimpregnated cutting posts 124 of the present invention may extendupwardly, wherein each discrete impregnated cutting post 124 may anglegenerally towards a front edge of the associated blade of the discreteimpregnated cutting post 124 and may angle generally towards thedirection of rotation of the rotary drag bit 100, (as shown in FIG. 1)on blades 118 from the bit face 116. The angle may be from 10 to 80degrees. Behind each discrete impregnated cutting post 124 may be amatrix pocket 236, 336 (shown in FIGS. 2, 3) supporting the discreteimpregnated cutting post 124. This may allow the discrete impregnatedcutting post 124 to be pushed to the front edge of the blade tofacilitate cooling and cleaning.

The discrete impregnated cutting posts 124, wear control elements 165,and PDCs may be integral parts of the blades 118 projecting from amatrix-type bit body 112 by hand-packing diamond-grit impregnated matrixmaterial in mold cavities on the interior of the bit mold defining thelocations of the discrete cutting structures 124 and the blades 118. Itis noted that the discrete cutting structures may be placed directly onthe bit face 116, dispensing with the blades. However, it is preferablethat the discrete cutting structures are located on the blades. It isalso noted that, while discussed in terms of being integrally formedwith the rotary drill bit 100, the discrete cutting structures may beformed as discrete individual segments, such as hot isostatic pressure,which are subsequently brazed or furnaced onto the rotary drill bit 100.

Discrete cutting structures may be mutually separated from each other,to promote drilling fluid flow therearound for enhanced cooling andclearing of formation material removed by the diamond grit. It is alsonoted that the rotary drill bit may comprise only one type of thediscrete impregnated cutting posts 124, wear control elements 165, andPDCs or may include combinations of two or more of the types of discretecutting structures.

FIG. 2 is an illustration of a schematic top elevation of portions of aplurality of blades of the rotary drill bit of FIG. 1 comprising aplurality of discrete impregnated cutting posts as is depicted inFIG. 1. Traditionally, discrete impregnated cutting post 224 inimpregnation bits would be placed in the center and supported by theblade 218. Unlike traditional impregnation bits, in the exemplaryembodiment depicted in FIG. 2, a matrix pocket 236 may be insertedbehind the discrete to support or house the discrete impregnated cuttingpost 224. This may allow the discrete impregnated cutting post 224 to bepushed to the front edge of the blade to facilitate cooling andcleaning. By including the matrix pocket 236, cooling and cleaning maybe increased by allowing fluid to flow over the discrete impregnatedcutting posts down the junk slot 222. Traditionally, flow was not aseffective because of the limited space between discrete cuttingprotrusions and distance from the junk slot 222. The embodiment shown inFIG. 2 may allow the fluid to better flow and thus cool the discretecutting structures, including the discrete impregnated cutting post 224due to it being located closer to the junk slot 222 and due to the spacecreated behind the discrete impregnated cutting post 224 and above thematrix pocket 236. The matrix pocket may be composed of superhardcutting elements, such as natural or synthetic diamond grit, dispersedwithin a matrix of wear resistant material or other suitable material toa person of skill in the art.

FIG. 3 is an illustration of a side sectional elevation of one of theplurality of blades of the rotary drill bit of FIG. 1 comprising one ofthe plurality of discrete impregnated cutting posts. Discreteimpregnated cutting post 324 is shown projecting at an angle generallytowards a front edge of the associated blade 318 of the discreteimpregnated cutting post 324 and may angle generally towards thedirection of rotation of the rotary drag bit 100, (as shown in FIG. 1)on blades 318.

Discrete impregnated cutting posts 324 may be generally of a round orcircular transverse cross-section at their substantially flat, outermostends 326. While the discrete impregnated cutting posts 324 areillustrated as exhibiting posts of circular outer ends, other geometriesare contemplated. For example, while not depicted in the figures, thediscrete impregnated cutting posts 324 may be configured as ovals havinga major diameter and a minor diameter. The base portion adjacent to theblade 318 might also be oval having a major and minor diameter whereinthe base has a larger minor diameter than the outermost end 326 of thediscrete impregnated cutting posts 324. As the discrete impregnatedcutting posts 324 wears towards the blade 318 the minor diameter mayincrease resulting in a larger surface area. Furthermore, the ends ofthe discrete impregnated cutting posts 324 may employ sloped geometries.In other words, the discrete impregnated cutting posts 324 may changecross sections at multiple intervals, and tip geometry may be separatefrom the general cross section of the cutting structure. Other shapes orgeometries may be configured similarly. It is also noted that thespacing between individual discrete impregnated cutting posts 324, aswell as the magnitude of the taper from the outermost ends 326 to theblades 318, may be varied to change the overall aggressiveness of therotary drill bit 100 (shown in FIG. 1) or to change the rate at whichthe bit is transformed from a light set bit to a heavy set bit duringoperation. It is further contemplated that one or more of such discreteimpregnated cutting posts 324 may be formed to have a substantiallyconstant cross-sections if so desired depending on the anticipatedapplication of the bit 100.

Discrete impregnated cutting posts 324 may comprise a synthetic diamondgrit, such as DSN-47 Synthetic diamond grit, commercially available fromDeBeers of Shannon, Ireland, which has demonstrated superior toughnessto natural diamond grit. The tungsten carbide matrix material with whichthe diamond grit is mixed to form discrete impregnated cutting posts 324and supporting blades 318 is preferably a fine grain carbide, such as,for example, DM2001 powder commercially available from Kennametal Inc.,of Latrobe, Pa. Such a carbide powder, when infiltrated, providesincreased exposure of the diamond grit particles in comparison toconventional matrix materials due to its relatively soft, abradablenature.

It is noted, however, that alternative particulate abrasive materialsmay be suitably substituted for those discussed above. For example, thediscrete impregnated cutting posts 324 may include natural diamond grit,a combination of synthetic and natural diamond grit. Alternatively, thecutting structures may include synthetic diamond pins.

FIG. 4 is an illustration of a side sectional elevation of one of theplurality of blades of the rotary drill bit of FIG. 1 comprising aplurality of discrete impregnated cutting posts. Discrete impregnatedcutting posts 424 may be angled generally towards a front edge of theassociated blade of the discrete impregnated cutting post 424 and mayangle generally towards the direction of rotation of the rotary dragbits thus creating a high backrake angle (shown in FIG. 3). Adding theone or more discrete impregnated cutting posts 424 at a high backratemay decrease the effective length of the discrete impregnated cuttingposts 424 when laying them out on the one or more blades 418. Therefore,additional clearance between the discrete impregnated cutting posts 424may be created and thus additional discrete impregnated cutting posts424 may be added to the one or more blades 418. As a result, the numberof discrete impregnated cutting posts 424 on a certain surface of a bitmay be increased thus improving the bits performance. This allows for anincrease in discrete impregnated cutting posts 424 density due to theincreased internal clearance. It should be appreciated that the each ofthe plurality of discrete cutting posts may be set at different backrakeangles to increase the density of the discrete impregnated cutting postsor increase the performance of the drill bit.

The increased backside rake angle 350 may provide other benefitsincluding allowing greater control of the wear rate of the rotary dragbit 100. By increasing the backside rake angle 350, the geometry of thematrix pocket 336 of the blade 418 may be controlled to add as muchtaper as is needed. This may allow the wear rate to be controlled basedon the rake angle and may improve the bits performance.

FIG. 5 is an illustration of a side sectional elevation of one of theplurality of blades of the rotary drill bit comprising a plurality ofdiscrete cutting protrusions which generally protrude perpendicular tothe blade. FIG. 5 illustrates how discrete cutting protrusions 524protruding generally perpendicularly to the blade 518 may not create theclearance and additional number of discrete impregnated cutting posts424 (shown in FIG. 4) that are created when the blades are at a highbackrake and thus angled generally towards a front edge of theassociated blade of the discrete impregnated cutting post 424 and mayangle generally towards the direction of rotation of the rotary dragbits thus creating a high backrake angle 350, as is shown in FIGS. 3, 4.

Other and further embodiments utilizing one or more aspects of theinventions described above can be devised without departing from thespirit of my/our invention. For example, wear control elements, PDCs,and other non-post discrete cutting structures may be included with thediscrete post posts of the present invention to create otherembodiments. Further, the various methods and embodiments of theimpregnation bit with improved cutting structure and blade geometry canbe included in combination with each other to produce variations of thedisclosed methods and embodiments. Discussion of singular elements caninclude plural elements and vice-versa.

The order of steps can occur in a variety of sequences unless otherwisespecifically limited. The various steps described herein can be combinedwith other steps, interlineated with the stated steps, and/or split intomultiple steps. Similarly, elements have been described functionally andcan be embodied as separate components or can be combined intocomponents having multiple functions.

The inventions have been described in the context of preferred and otherembodiments and not every embodiment of the invention has beendescribed. Obvious modifications and alterations to the describedembodiments are available to those of ordinary skill in the art. Thedisclosed and undisclosed embodiments are not intended to limit orrestrict the scope or applicability of my/our invention, but rather, inconformity with the patent laws, I/we intend to fully protect all suchmodifications and improvements that come within the scope or range ofequivalent of the following claims.

1. A rotary drag bit for drilling subterranean formations comprising: abit body having a face extending from a centerline to a gage; aplurality of blades on the face generally extending radially outwardlytoward the gage; a plurality of discrete impregnated cutting posts, andwherein each discrete impregnated cutting post extends outwardly from anassociated one of the plurality of blades; and wherein each discreteimpregnated cutting post angles generally towards a front edge of theassociated blade of the discrete impregnated cutting post and generallytowards a direction of a rotation of the rotary drag bits.
 2. The rotarydrag bit of claim 1, further comprising a plurality of matrix pocketsdisposed on the plurality of blades, wherein each discrete impregnatedcutting post is housed within an associated one of the plurality ofmatrix pockets.
 3. The rotary drag bit of claim 2, wherein each matrixpocket supports the associated discrete impregnated cutting post.
 4. Therotary drag bit of claim 1, wherein the matrix pocket facilitatescooling and cleaning.
 5. The rotary drag bit of claim 1, furthercomprises one or more of polycrystalline diamond compact (PDC) cutters.6. The rotary drag bit of claim 1, wherein the plurality of discreteimpregnated cutting posts and the plurality of blades are integrallyformed.
 7. The rotary drag bit of claim 1, wherein the plurality ofdiscrete impregnated cutting posts comprises a particulate abrasivematerial.
 8. The rotary drag bit of claim 1, wherein the bit bodycomprises a matrix-type bit body.
 9. The rotary drag bit of claim 1,wherein the plurality of discrete impregnated cutting posts are formedof a material comprising a thermally stable diamond product (TSP). 10.The rotary drag bit of claim 1, wherein the plurality of blades on theface generally extending radially outwardly in a generally perpendiculardirection from a surface of the bit body.
 11. The rotary drag bit ofclaim 8, wherein the particulate abrasive material comprises at leastone of synthetic diamond grit and natural diamond grit.
 12. A method offorming a rotary drag bit for drilling subterranean formationscomprising: forming a body having a centerline and face extending from acenterline to a gage; forming a plurality of blades on the facegenerally extending radially outwardly toward the gage; and forming aplurality of discrete impregnated cutting posts, wherein each discreteimpregnated cutting post extends outwardly from an associated one of theplurality of blades; and wherein each discrete impregnated cutting postangles generally towards a front edge of the associated blade of thediscrete impregnated cutting post and generally towards a direction of arotation of the rotary drag bits.
 13. The method of claim 12, furthercomprising forming a plurality of matrix pockets disposed on theplurality of blades, wherein each discrete impregnated cutting post ishoused within an associated one of the plurality of matrix pockets. 14.The method of claim 12, wherein each matrix pocket is formed to supportthe associated discrete impregnated cutting post of the matrix pocket.15. The method of claim 12, wherein the matrix pocket facilitatescooling and cleaning.
 16. The method of claim 12, further comprisingintegrally forming the plurality of discrete impregnated cutting postsand the plurality of blades.
 17. The method of claim 12, wherein eachdiscrete impregnated cutting post is angled to prevent wear rate.